The present invention relates to automotive vehicles, and more particularly to powertrain control of automotive vehicles.
Transmissions are known that have over-running, or one-way clutches. In some applications, these clutches are used to enable certain types of vehicle shifts such as so-called non-synchronous gear changes. In some cases, the transmission input speed is less than the synchronous speed of the selected gear during situations in which the clutch is over-running. To prevent such situations, an electric motor, coupled to the transmission through a torque synthesizing/distributing unit, is used to maintain the gear input speed at or near the synchronous speed. The torque synthesizing/distributing unit is an additional unit that has planetary gear sets and several clutches. Such a system is described in U.S. Pat. No. 6,019,699.
The inventors herein have recognized a disadvantage with the above approach. In particular, such a method uses an electric motor, which is not available on the majority of mass production vehicles. Adding such a motor can be a significant additional cost to the customer. Further, the above method also uses an additional torque synthesizing/distributing unit. This additional device adds further to the cost of the vehicle.
The disadvantages of prior approaches are overcome by a method for controlling an engine coupled to a transmission having at least one gear in which an over-running clutch is present, the transmission having an input speed and an output speed. The method comprises determining a synchronous transmission input speed based on the transmission state and the transmission output speed, indicating whether a current gear is a gear in which an over-running clutch is present; and in response to said indication, adjusting an engine operating parameter to maintain the transmission input speed at or below said synchronous transmission input speed.
By adjusting an engine operating to maintain the transmission input speed at or below said synchronous transmission input speed, it is possible to prevent tip-in torque shock, without the additional cost of an electric motor and an addition torque synthesizing/distributing unit.
Advantages of the present invention are improved drivability and reduced cost.
It is important to note that various parameters can be used to indicate transmission output speed such as, for example, vehicle speed or output shaft speed. Further various engine operating parameters can be used such as, for example, engine airflow, engine torque, ignition timing, engine air/fuel, and various others.